This treemap visualizes U.S. steel scrap export values by partner country and commodity, using area size and a light-to-dark blue color scale to encode magnitude. Clicking a country drilils down to show individual commodity values, while a reset button restores the top-level view. The D3 v7 implementation uses d3.hierarchy, d3.treemap, and d3.scaleSequential with interpolateRgb, rendering SVG rectangles with transitions and tooltips via title elements. Data comes from a CSV file with partner country, commodity description, and value fields.